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Scleromochlus and the early evolution of Pterosauromorpha


Pterosaurs, the first vertebrates to evolve powered flight, were key components of Mesozoic terrestrial ecosystems from their sudden appearance in the Late Triassic until their demise at the end of the Cretaceous1,2,3,4,5,6. However, the origin and early evolution of pterosaurs are poorly understood owing to a substantial stratigraphic and morphological gap between these reptiles and their closest relatives6, Lagerpetidae7. Scleromochlus taylori, a tiny reptile from the early Late Triassic of Scotland discovered over a century ago, was hypothesized to be a key taxon closely related to pterosaurs8, but its poor preservation has limited previous studies and resulted in controversy over its phylogenetic position, with some even doubting its identification as an archosaur9. Here we use microcomputed tomographic scans to provide the first accurate whole-skeletal reconstruction and a revised diagnosis of Scleromochlus, revealing new anatomical details that conclusively identify it as a close pterosaur relative1 within Pterosauromorpha (the lagerpetid + pterosaur clade). Scleromochlus is anatomically more similar to lagerpetids than to pterosaurs and retains numerous features that were probably present in very early diverging members of Avemetatarsalia (bird-line archosaurs). These results support the hypothesis that the first flying reptiles evolved from tiny, probably facultatively bipedal, cursorial ancestors1.

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Fig. 1: Newly revealed anatomical features of S. taylori.
Fig. 2: Comparisons of selected features of S. taylori and pterosauromorphs.
Fig. 3: Time-calibrated strict consensus tree focused on Pterosauromorpha and different positions of S. taylori based on interpretations of the phylogenetic scores for the ankle.
Fig. 4: Digital 3D life reconstruction of S. taylori.

Data availability

The taxon–character data matrices for the phylogenetic analyses for TNT and MrBayes are available in Nexus and TNT formats in the Supplementary Information and in MorphoBank at The µCT datasets and videos of the six specimens of S. taylori are available in MorphoSource at (the videos are also available as Supplementary Information files).


  1. Padian, K. in Third Symposium on Mesozoic Terrestrial Ecosystems Tübingen 1984 Short Papers (eds Reif, W.-E. & Westphal, F.) 163–168 (Tübingen Attempto, 1984).

  2. Padian, K. The origins and aerodynamics of flight in extinct vertebrates. Palaeontology 28, 413–433 (1985).

    Google Scholar 

  3. Witton, M. P. Pterosaurs: Natural History, Evolution, Anatomy (Princeton Univ. Press, 2013).

  4. Sereno, P. C. Basal archosaurs: phylogenetic relationships and functional implications. Soc. Vertebr. Paleontol. Mem. 2, 1–53 (1991).

    Article  Google Scholar 

  5. Benton, M. J. Scleromochlus taylori and the origin of dinosaurs and pterosaurs. Phil. Trans. R. Soc. Lond. B 354, 1423–1446 (1999).

    Article  Google Scholar 

  6. Dalla Vecchia, F. M. in Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin (eds Nesbitt, S. J. et al.) 119–155 (Geological Society London, 2013).

  7. Ezcurra, M. D. et al. Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria. Nature 588, 445–449 (2020).

    Article  ADS  CAS  PubMed  Google Scholar 

  8. von Huene, F. Beiträge zur Geschichte der Archosaurier. Geologische und Palaeontologische Abhandlungen. Neue Folge 13, 1–53 (1914).

    Google Scholar 

  9. Bennett, S. C. Reassessment of the Triassic archosauriform Scleromochlus taylori: neither runner nor biped, but hopper. PeerJ 8, e8418 (2020).

    Article  PubMed  PubMed Central  Google Scholar 

  10. Woodward, A. S. On a new dinosaurian reptile (Scleromochlus Taylori, gen. et sp. nov.) from the Trias of Lossiemouth, Elgin. Q. J. Geol. Soc. Lond. 63, 140–144 (1907).

    Article  Google Scholar 

  11. Benton, M. J. & Walker, A. D. Palaeoecology, taphonomy, and dating of Permo-Triassic reptiles from Elgin, north-east Scotland. Palaeontology 28, 207–234 (1985).

    Google Scholar 

  12. Foffa, D. et al. Revision of Erpetosuchus (Archosauria: Pseudosuchia) and new erpetosuchid material from the Late Triassic ‘Elgin reptile’ fauna based on μCT scanning techniques. Earth Environ. Sci. Trans. R. Soc. Edinb. 111, 209–233 (2020).

    Google Scholar 

  13. Nesbitt, S. J. et al. The earliest bird-line archosaurs and the assembly of the dinosaur body plan. Nature 544, 484–487 (2017).

    Article  ADS  CAS  PubMed  Google Scholar 

  14. Gauthier, J. A. in The Origin of Birds and the Evolution of Flight, Memoirs of the California Academy of Sciences Vol. 8 (ed. Padin, K.) 1–55 (California Academy of Sciences, 1986).

  15. Desojo, J. B., et al. in Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and their Kin (eds Nesbitt, S. J. et al.) 203–239 (Geological Society London, 2013).

  16. Nesbitt, S. J. The early evolution of archosaurs: relationships and the origin of major clades. Bull. Am. Mus. Nat. Hist. 352, 1–292 (2011).

    Article  Google Scholar 

  17. Ezcurra, M. D. The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. PeerJ 4, e1778 (2016).

    Article  PubMed  PubMed Central  Google Scholar 

  18. Kellner, A. W. A. Comments on Triassic pterosaurs with discussion about ontogeny and description of new taxa. An. Acad. Bras. Cienc. 87, 669–689 (2015).

    Article  PubMed  Google Scholar 

  19. Dzik, J. A beaked herbivorous archosaur with dinosaur affinities from the early Late Triassic of Poland. J. Vertebr. Paleontol. 23, 556–574 (2003).

    Article  Google Scholar 

  20. Padian, K. Were pterosaur ancestors bipedal or quadrupedal? Morphometric, functional, and phylogenetic considerations. Zitteliana B28, 21–33 (2008).

    Google Scholar 

  21. Yáñez, I., Pol, D., Leardi, J. M., Alcober, O. A. & Martínez, R. N. An enigmatic new archosauriform from the Carnian–Norian, Upper Triassic, Ischigualasto Formation of northwestern Argentina. Acta Palaeontol. Pol. 66, 509–533 (2021).

    Article  Google Scholar 

  22. McCabe, M. B., Mason, B. & Nesbitt, S. J. The first pectoral and forelimb material assigned to the lagerpetid Lagerpeton chanarensis (Archosauria: Dinosauromorpha) from the upper portion of the Chañares Formation, Late Triassic. Palaeodiversity 14, 121–131 (2021).

    Article  Google Scholar 

  23. Müller, R. T., Langer, M. C. & Dias-da-Silva, S. Ingroup relationships of Lagerpetidae (Avemetatarsalia: Dinosauromorpha): a further phylogenetic investigation on the understanding of dinosaur relatives. Zootaxa 4392, 149–158 (2018).

    Article  PubMed  Google Scholar 

  24. Irmis, R. B. et al. A late Triassic dinosauromorph assemblage from New Mexico and the rise of dinosaurs. Science 317, 358–361 (2007).

    Article  ADS  CAS  PubMed  Google Scholar 

  25. Kammerer, C. F., Nesbitt, S. J., Flynn, J. J., Ranivoharimanana, L. & Wyss, A. R. A tiny ornithodiran archosaur from the Triassic of Madagascar and the role of miniaturization in dinosaur and pterosaur ancestry. Proc. Natl Acad. Sci. USA 117, 17932–17936 (2020).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  26. Sereno, P. C. & Arcucci, A. B. Dinosaurian precursors from the Middle Triassic of Argentina: Lagerpeton chanarensis. J. Vertebr. Paleontol. 13, 385–399 (1994).

    Article  Google Scholar 

  27. Hone, D. W. E., Tischlinger, H., Frey, E. & Röper, M. A new non-pterodactyloid pterosaur from the Late Jurassic of southern Germany. PLoS ONE 7, e39312 (2012).

    Article  ADS  CAS  PubMed  PubMed Central  Google Scholar 

  28. Demuth, O. E., Rayfield, E. J. & Hutchinson, J. R. 3D hindlimb joint mobility of the stem-archosaur Euparkeria capensis with implications for postural evolution within Archosauria. Sci. Rep. 10, 15357 (2020).

    Article  ADS  PubMed  PubMed Central  Google Scholar 

  29. Barrett, P. M. & Maidment, S. C. R. The evolution of ornithischian quadrupedality. J. Iber. Geol. 43, 363–377 (2017).

    Article  Google Scholar 

  30. Padian, K. A functional analysis of flying and walking in pterosaurs. Paleobiology 9, 218–239 (1983).

    Article  Google Scholar 

  31. Kubo, T. & Kubo, M. O. Associated evolution of bipedality and cursoriality among Triassic archosaurs: a phylogenetically controlled evaluation. Paleobiology 38, 474–485 (2012).

    Article  Google Scholar 

  32. Campione, N. E., Evans, D. C., Brown, C. M. & Carrano, M. T. Body mass estimation in non-avian bipeds using a theoretical conversion to quadruped stylopodial proportions. Methods Ecol. Evol. 5, 913–923 (2014).

    Article  Google Scholar 

  33. Britt, B. B. et al. Caelestiventus hanseni gen. et sp. nov. extends the desert-dwelling pterosaur record back 65 million years. Nat. Ecol. Evol. 2, 1386–1392 (2018).

    Article  PubMed  Google Scholar 

  34. Behrensmeyer, A. K. et al. Taphonomy and paleocommunity reconstruction of a pterosaur-bearing fossil assemblage in the Upper Triassic of Arizona. J. Vertebr. Paleontol. Program and Abstracts 61, 60 (2019).

  35. Jenkins, F. A. Jr, Shubin, N. H., Gatesy, S. M. & Padian, K. A diminutive pterosaur (Pterosauria: Eudimorphodontidae) from the Greenlandic Triassic. Bull. Mus. Comp. Zool. 156, 151–170 (2001).

    Google Scholar 

  36. Martínez, R. N., Andres, B., Apaldetti, C. & Cerda, I. A. The dawn of the flying reptiles: first Triassic record in the southern hemisphere. Pap. Palaeontol. 8, e1424 (2022).

    Article  Google Scholar 

  37. Simms, M. J. & Ruffell, A. H. Synchroneity of climatic change and extinctions in the Late Triassic. Geology 17, 265–268 (1989).

    Article  ADS  Google Scholar 

  38. Roghi, G., Gianolla, P., Minarelli, L., Pilati, C. & Preto, N. Palynological correlation of Carnian humid pulses throughout western Tethys. Palaeogeogr. Palaeoclimatol. Palaeoecol. 290, 89–106 (2010).

    Article  Google Scholar 

  39. Benton, M. J., Bernardi, M. & Kinsella, C. The Carnian Pluvial episode and the origin of dinosaurs. J. Geol. Soc. 175, 1019–1026 (2018).

    Article  ADS  Google Scholar 

  40. Dunne, E. M., Farnsworth, A., Greene, S. E., Lunt, D. J. & Butler, R. J. Climatic drivers of latitudinal variation in Late Triassic tetrapod diversity. Palaeontology 64, 101–117 (2020).

    Article  Google Scholar 

  41. Liu, J., Angielczyk, K. D. & Abdala, F. Permo-Triassic tetrapods and their climate implications. Glob. Planet. Change 205, 103618 (2021).

    Article  Google Scholar 

  42. Chiarenza, A. A., Mannion, P. D., Farnsworth, A., Carrano, M. & Varela, S. Climatic constraints on the biogeographic history of Mesozoic dinosaurs. Curr. Biol. 32, 570–585 (2022).

    Article  CAS  PubMed  Google Scholar 

  43. Mancuso, A. C. et al. Paleoenvironmental and biotic changes in the Late Triassic of Argentina: testing hypotheses of abiotic forcing at the basin scale. Front. Earth Sci. 10, 883788 (2022).

    Article  ADS  Google Scholar 

  44. Kellner, A. W. A. Remarks on pterosaur taphonomy and paleoecology. Acta Geol. Leopold. 39, 175–189 (1994).

    Google Scholar 

  45. Dean, C. D., Mannion, P. D. & Butler, R. J. Preservational bias controls the fossil record of pterosaurs. Palaeontology 59, 225–247 (2016).

    Article  PubMed  PubMed Central  Google Scholar 

  46. Davies, T. G. et al. Open data and digital morphology. Proc. R. Soc. B 284, 20170194 (2017).

    Article  PubMed  PubMed Central  Google Scholar 

  47. Ezcurra, M. D. et al. Deep faunistic turnovers preceded the rise of dinosaurs in southwestern Pangaea. Nat. Ecol. Evol. 1, 1477–1483 (2017).

    Article  PubMed  Google Scholar 

  48. Ezcurra, M. D. & Butler, R. J. The rise of the ruling reptiles and ecosystem recovery from the Permo-Triassic mass extinction. Proc. R. Soc. B 285, 20180361 (2018).

    Article  PubMed  PubMed Central  Google Scholar 

  49. Butler, R. J. et al. Cranial anatomy and taxonomy of the erythrosuchid archosauriform ‘Vjushkovia triplicostata’ Huene, 1960, from the Early Triassic of European Russia. R. Soc. Open Sci. 6, 191289 (2019).

    Article  ADS  PubMed  PubMed Central  Google Scholar 

  50. Spiekman, S. N. F., Ezcurra, M. D., Butler, R. J., Fraser, N. C. & Maidment, S. C. R. Pendraig milnerae, a new small-sized coelophysoid theropod from the Late Triassic of Wales. R. Soc. Open Sci. 8, 210915 (2021).

    Article  ADS  PubMed  PubMed Central  Google Scholar 

  51. Goloboff, P. A., Farris, J. S. & Nixon, K. C. TNT, a free program for phylogenetic analysis. Cladistics 24, 774–786 (2008).

    Article  Google Scholar 

  52. Goloboff, P. A. & Catalano, S. A. TNT version 1.5, including a full implementation of phylogenetic morphometrics. Cladistics 32, 221–238 (2016).

    Article  PubMed  Google Scholar 

  53. Ronquist, F., van der Mark, P. & Huelsenbeck, J. P. in The Phylogenetic Handbook: a Practical Approach to Phylogenetic Analysis and Hypothesis Testing (eds Lemey, P. et al.) 210–266 (Cambridge Univ. Press, 2009).

  54. Benton, M. J. et al. Constraints on the timescale of animal evolutionary history. Palaeontol. Electronica 18, 1–106 (2015).

    Google Scholar 

  55. Ezcurra, M. D., Scheyer, T. M. & Butler, R. J. The origin and early evolution of Sauria: reassessing the Permian saurian fossil record and the timing of the crocodile-lizard divergence. PLoS ONE 9, e89165 (2014).

    Article  ADS  PubMed  PubMed Central  Google Scholar 

  56. Benton, M. J. & Walker, A. D. Erpetosuchus, a crocodile-like basal archosaur from the Late Triassic of Elgin, Scotland. Zool. J. Linn. Soc. 136, 25–47 (2002).

    Article  Google Scholar 

  57. Bernardi, M., Gianolla, P., Petti, F. M., Mietto, P. & Benton, M. J. Dinosaur diversification linked with the Carnian Pluvial episode. Nat. Commun. 9, 1499 (2018).

    Article  ADS  PubMed  PubMed Central  Google Scholar 

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We thank V. Fernandez, T. G. Davies and E. G. Martin-Silverstone for scanning the specimens; A. A. Chiarenza for discussion and assistance; G. Ugueto for creating the artwork that accompanies this paper; M. Humpage for the 3D reconstruction of the skeleton; A. Fitch for sharing the photograph of Raeticodactylus used in Fig. 2; and S. Hartman for permission to use silhouettes from This study was supported by the Royal Commission for the Exhibition of 1851–Science Fellowship awarded to D.F. R.J.B., E.M.D., A.F., D.J.L. and P.J.V. were supported by a Leverhulme Research Project Grant (RPG-2019-365).

Author information

Authors and Affiliations



D.F. designed the project with input from N.C.F., S.W., R.J.B., S.L.B. and P.M.B. D.F. processed the μCT data and described the material. D.F., with the assistance of S.J.N. and P.M.B., scored the phylogenetic matrices and conducted the phylogenetic analyses. D.F. wrote the bulk of the manuscript and created the figures. P.M.B. conducted sedimentological tests on the specimens. All authors contributed to the writing, discussions and conclusions.

Corresponding author

Correspondence to Davide Foffa.

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The authors declare no competing interests.

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Nature thanks Hans Dieter-Sues, Martin Ezcurra, Lawrence Tanner and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Extended data figures and tables

Extended Data Fig. 1 Life reconstruction of Scleromochlus taylori.

Artwork by Gabriel Ugueto (high-resolution version).

Extended Data Fig. 2 Digital rendering of Scleromochlus taylori specimens from µCT scans.

Holotype NHMUK PV R3556, dorsal view (top left); NHMUK PV R3557, ventral view (right); NHMUK PV R3914, ventral view (bottom left). Red shading highlights the skeleton traces on the digital peels, while solid red rendering indicates previously unknown body parts.

Extended Data Fig. 3 Strict consensus phylogenetic tree of analysis including indeterminate ankle scores.

Absolute and present/contradicted group bootstrap frequencies (respectively left and right above the branches) and Bremer support values (below the branches). Note that in ~95% of the most parsimonious trees Scleromochlus is found as the earliest-diverging lagerpetid (it is alternatively found as the earliest-diverging member of a lagerpetid clade also composed of Ixalerpeton, Kongonaphon and Lagerpeton).

Extended Data Fig. 4 Strict consensus phylogenetic tree of analysis using scores for an advanced fused mesotarsal ankle.

Absolute and present/contradicted group bootstrap frequencies (respectively left and right above the branches) and Bremer support values (below the branches). Note that in ~95% of the most parsimonious trees Scleromochlus is found as the earliest-diverging lagerpetid (it is alternatively found as the earliest-diverging member of a lagerpetid clade also composed of Ixalerpeton, Kongonaphon and Lagerpeton).

Extended Data Fig. 5 Strict consensus phylogenetic tree of analysis using scores for an “intermediate” mesotarsal ankle.

Absolute and present/contradicted group bootstrap frequencies (respectively left and right above the branches) and Bremer support values (below the branches).

Extended Data Fig. 6 Strict consensus phylogenetic tree of analysis based on scores for a crurotarsal ankle.

Absolute and present/contradicted group bootstrap frequencies (respectively left and right above the branches) and Bremer support values (below the branches).

Extended Data Fig. 7 Bayesian inference convergence topology trees.

The position of Scleromochlus taylori remains the same regardless of the scoring strategy of the ankle. The alternative topology within Pterosauria is found only when using the ‘crurotarsal ankle’ settings.

Extended Data Table 1 Table of measurements

Supplementary information

Supplementary Information

This file contains Supplementary Table of Contents; a URL containing a link to access Supplementary Datasets; Historical background; legends for Supplementary Videos and Supplementary References

Reporting Summary

Supplementary Video 1

Supplementary Video 2

Supplementary Video 3

Supplementary Video 4

Supplementary Video 5

Supplementary Video 6

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Foffa, D., Dunne, E.M., Nesbitt, S.J. et al. Scleromochlus and the early evolution of Pterosauromorpha. Nature 610, 313–318 (2022).

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